Their latest novels take place in settings literally worlds away from each other -- beyond the farthest reaches of our solar system and in a near-future American Southwest ravaged by drought and greed. Nevertheless, award-winning science fiction writers Kim Stanley Robinson and Paolo Bacigalupi share a deep commitment to the here-and-now and the environmental concerns facing humanity this Earth Day and for the foreseeable future.

On April 20, Robinson and Bacigalupi will appear in conversation at Kepler's Books in Menlo Park. They will discuss and sign the paperback editions of their latest novels, "Aurora" and "The Water Knife."

Reached in a telephone conference call, Robinson and Bacigalupi already shared an easy rapport, picking up each other's verbal cues without much prompting from the interviewer.

"For whatever reason, we seem to be science fiction writers who are engaged with the natural world," Bacigalupi said. "And that's something of a rarity, oddly. Science fiction is really, really excited about the toys, and not so excited about the people or the biosphere."

Robinson, 64, resides in Davis, California and is the author of 17 novels, including the acclaimed "Mars Trilogy" set on a terraformed Red Planet. He's written about the environmental challenges facing the southern-most continent in "Antarctica" and addressed global warming and its catastrophic effects on Washington, D.C., in the "Science in the Capital" trilogy, recently shortened and collected in one volume as "Green Earth."

Bacigalupi, 43, made his mark on science fiction with the Hugo and Nebula Award-winning "The Wind-up Girl," set in a post-petroleum, bioengineered Thailand. A resident of western Coloado, he has written eco-thrillers for teens -- including "The Drowned Cities" and "Zombie Baseball Beatdown" -- and his latest novel for adults, "The Water Knife," uses the conventions of detective fiction to chronicle the machinations of fixers, journalists and refugees when they're caught in Nevada and Arizona's fight over dwindling water supplies.

Science fiction and literary fiction have both taken a strong turn toward the apocalyptic lately. Some authors destroy civilization with zombies, vampires and deadly viruses, while others choose more realistic depictions of the consequences of drought, sea-level elevation and extreme weather.

"I think dystopia and utopia are two sides of the same literary impulse, and they should always be paired together," Robinson said. "Utopias express our hopes, and dystopias express our fears."

Although siding with the utopians, Robinson said he understands why dystopian fiction is popular now.

"It's kind of a fearful time, which is a rational response to the certainty of climate change coming down on us," he said. "Global average temperature figures for February were just astonishing. That was the only word scientists could use for it, because (the figures) had jumped so fast so far."

In the face of that kind of sudden, alarming change, Robinson said his "whole angle has been to ask, 'What will the utopian response be?' I more and more feel like I'm providing fantasy solutions. But since it is fiction, you get to do that. So I write down these positive scenarios and say, 'Gosh, I don't know whether this is likely or not, but let's make it look as likely as possible.' That's the literary trick of it."

Bacigalupi said, "I think the biggest difference between my writing and Stan's is that he's looking at us as human beings and saying, 'We have the capacity to make smart, effective choices. Certainly, we don't have to be just dysfunctional.' And he's right."

Bacigalupi said to Robinson, "I'm not so sure that I think you write fantasy as you do focus on the slice of humanity that is actually decent or has some drive toward decency. Whereas I keep focusing on the worst aspects of it."

Even those worst aspects can still be instructive. Bacigalupi said that one of the most satisfying things about "The Water Knife" isn't that "it's necessarily going to cause somebody to go out and stop Aquafina from privatizing aquifiers. But people will have context for understanding their natural world a little better."

In discussing encounters with readers on Twitter, Bacigalupi said, "When somebody sees a photo of Lake Mead, and it's drawn down to the extent it is now, then they suddenly connect that to the broken world that is 'The Water Knife.' They're like, "Oh my god! Look at this low reservoir!" And I'm like 'Yes! Now you're just as frightened of this as I am!'"

Does that kind of revelation promote an immediate change in people's behavior?

"No, I don't think it does," Bacigalupi said. "But it does provide a counterpoint to the idea of 'I just got my new iPhone and all is good in the world.'"

Robinson also hears from worried readers. (He said that, thanks to the "Science in the Capital" trilogy, "Every time there's a big storm in Washington, D.C. I get a ton of emails. 'Oh god, it's all happening!'") Set aboard a spaceship that will take generations to reach its destination, his new novel, "Aurora," has received a wide variety of responses "including some really, really angry ones." The book makes the case that humanity won't be saved by a mass exodus from Earth, that we had better save the one planet we've got, rather than try to settle in another solar system.

For science fiction readers heavily invested in the notion of interstellar travel, the idea that it might not be easy or even possible can be the equivalent of "taking their most favorite plastic toy and smashing it with a baseball bat repeatedly," Robinson said.

"I've seen reactions all over the map. But that's why I wrote the book in the first place. None of (the objections) are very convincing. I think the universe is on my side in this particular argument."

Neither Robinson nor Bacigalupi believes in science fiction's ability to predict the future accurately. But both see the value in thinking about the implications of possible new scenarios before they arrive.

"I do that stuff in my own personal life as a writer," Bacigalupi said, "where I'm looking at massive changes in the publishing industry. It's like, 'OK, where do you need to be in 10 years if you still think you want to be a writer creating these kinds of stories about these issues?'" Although he believes one can't accurately predict outcomes, "you can prepare for all these kinds of scenarios and have bets on the table."